1. Field of the Invention
This invention relates to a process for preparing glass fiber mats. More particularly, this invention relates to a process for preparing glass fiber mats in which the binder resin dissolves rapidly in vinyl monomers.
2. Description of the Prior Art
Glass fiber mats are widely used as reinforcements for fiber-reinforced plastics (FRP). Powders of unsaturated polyester resins have heretofore been used as binders for such glass fiber mats. When a powder of such unsaturated polyester resin is scattered on the glass fibers and the fibers are placed in an oven, the resin is melted and functions to bind the glass fibers to one another. In this manner, glass fiber mats are prepared on an industrial scale. A variety of glass fiber mats which differ in the rates of dissolution of their binder resins in vinyl monomers are required, depending on the molding methods for producing the FRP products. Further, glass fiber mats should have a tensile strength sufficient to withstand the molding operation. It is also required that the binder resin for glass fiber mats should have the property that a minimum amount thereof will impart a maximum strength to the mats.
As a means for lowering the rate of dissolution of binder resins in vinyl monomers, there has heretofore been adopted a method comprising incorporating in an unsaturated polyester resin from 1 to 3 wt. percent of a catalyst such as benzoyl peroxide and heating a mat impregnated therewith in an oven to cause a cross-linking reaction in the resin. As a means for increasing the dissolution rate, there has been adopted a method in which the chemical composition of the unsaturated polyester resin is changed. However, when an unsaturated polyester resin alone is used as the binder, it is essentially impossible to increase the rate of dissolution of the binder in vinyl monomers beyond a certain limit.
It is therefore a primary object of this invention to provide a process for preparing glass fiber mats using a binder resin having a very high rate of dissolution in vinyl monomers.